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Biomedical subjects

E L von Wallenberg

Publications and source records attributed to E L von Wallenberg.

8 recordsLinked to original sources
PubMed1991

Comparative speech recognition results in eight subjects using two different coding strategies with the Nucleus 22 channel cochlear implant.

This study was designed to compare the results of several speech tests administered to eight subjects who used two types of speech-coding strategies with the Nucleus 22 channel cochlear implant. The subjects had an average experience of 40 months with the F0F1F2 coding strategy implemented in their previous wearable speech processor. Three subjects were good performers (showing significant open-set understanding without lip-reading) and five were moderate performers (not able to do speech-tracking by auditory means alone). All subjects were evaluated again after 1 month and 6 months of experience with the MULTIPEAK coding strategy of the miniature speech processor. The test materials included vowel and consonant identification, monosyllabic words, everyday sentences and numbers in noise. All eight subjects showed an improvement on more than three of five measures. The group of moderate performers showed a larger improvement in vowel (+16%) and consonant (+17%) identification scores than the group of good performers. For the open-set sentence test, the better patients were able to increase their score from 52% to 80% correct; two of the moderate performers did not improve. Six subjects achieved significantly higher scores at moderate signal-to-noise ratios (up to 10 dB S/N) in the (Freiburger) number test. Results of information transmission analysis are also discussed.

Acoustic Stimulation↗
PubMed1990

Initial results with simultaneous analog and pulsatile stimulation of the cochlea.

An improved method has been developed for the coding of speech information into adequate signals for the stimulation of the auditory nerve. It combines the periodicity principle, which has been applied in single-channel analog stimulation in the Austrian cochlear prosthesis, with the place principle by simultaneous analog stimulation on one channel and pulsatile stimulation on other channels. The second formant frequency determines the place of stimulation for the pulsatile signals. Simultaneous stimulation of several channels can cause the currents emerging from different electrodes to interact because the fluid impedance in the cochlea is small. Therefore, an important aspect of the multichannel strategy is to maintain the temporal pattern transmitted via the analog channel by adequate repetition rates and phase relationships of the pulsatile signals. The signals were processed with finite impulse response digital filters. Vowel identification tests were performed with 6 patients implanted with a 4-channel intracochlear electrode. The test material was spoken by male and female speakers. With proper timing of the pulses the improvement over the single-channel stimulation was significant at the 1% level and this difference was due to a significant increase in second formant recognition.

Cochlear Implants↗